I figure about 3 to 4 cents per round for powder cost. It depends on the load used and the cost of the powder. This should be a ball park figure. Primers about 3 cents or less depending on where you buy them and how many you get at a time. The big cost is the bullet. I get my cases from factory ammo I have shot so I seldom ever include the cost of the case. It isn't unusual to be able to load pistol ammo for half the cost of factory ammo when you buy components in bulk. Cases normally can be used several times. Even if you did buy them, you have to figure the cost of a case over its life. An example would be, if a case is normally used 20 times then the cost of the case for one loading would be 1/20 the cost of the original price.
Many reloaders taylor their reloads to what they want (heavy to light loads) and get accuracy normally reserved for premium ammo. Most also compare the cost saved to the cheapest ammo available for a given round. I think it should be compared to the better ammo out there once you have a load dialed in for your needs. This makes the savings more realistic in my opinion.
I do have factory ammo for SD/HD use, but it seldom gets shot at the range.